Honda BF50 (5HP) BF5A Outboard Motors Shop Manual., Page 42Get this manual
b, INSPECTION VALVE SPRING FREE LENGTH
Measure the free length of the valve springsSTANDARD SERVICE T
29.0 mrn (1.142 in)
28.1 (1.106 in)
Replace the springs if they are shorter than the service limk
VALVE SEAT WIDTH
Measure the valve seat h
STANDAR 0.8 mm (0.031 in)
SERVICE T
1.8 (0.07 in)
If the valve seat width is under the standard, or over the service limit, recondition the valve seat(P.44)
CYLINDER HEAD
Remove carbon deposits from the combustion chamberClean any gasket material from the cylinder head surfaceCheck the spark plug hole and valve areas cracksCheck the cylinder head for warpage with straight edge and feeicier gauge